The first implication for management from this topic is that the primary purpose of a network is to provide a worry-free environment in which applications can run. The network itself does not change the way an organization operates; it is the applications that the network enables that have the potential to change organizations. If the network does not easily enable a wide variety of applications, this can severely limit the ability of the organization to compete in its environment.
The second implication is that over the past few years there has been a dramatic increase in the number and type of applications that run across networks. In the early 1990s, networks primarily delivered e-mail and organization-specific application traffic (e.g. accounting transactions, database inquiries, inventory data). Today’s traffic contains large amounts of e-mail, Web packets, videoconferencing, telephone calls, instant messaging, music, and organization-specific application traffic. Traffic has been growing much more rapidly than expected and each type of traffic has different implications for the best network design, making the job of the network manager much more complicated. Most organizations have seen their network operating costs grow significantly even though the cost per packet (i.e., the cost divided by the amount of traffic) has dropped significantly over the last ten years.
Meet Virtual Margaret
MANAGEMENT FOCUS
Margaret worked for Cisco Systems, Inc., in San Jose, California, for three years as the executive assistant to Martin de Beer, the vice president of the emerging markets group. With the rising cost of living in the San Jose, she decided to move to Dallas, Texas. Margaret didn’t want to leave Cisco, and Cisco didn’t want to lose her. However, her job as an executive assistant required regular face-to-face interaction with her boss and the other members of the team.
The solution was telepresence. Cisco installed a 65-inch high-definition plasma screen, a camera, microphone, speaker, and lighting array at her desk in San Jose, and at her desk in Dallas. When she arrives at work in Dallas, she connects to her desk in San Jose and begins her day. She is immediately available to all who pass her desk — in either location. Cisco installed a second telepresence unit in the conference room in San Jose, so with a push of a button, Margaret can join any meeting in the conference room.
”In the beginning, there were a lot of people stopping by,” she says. ”Mouths would drop open when people saw me, as if in disbelief and amazement of what they were seeing. Now, as folks get used to seeing me day in and day out, it is business as usual. One interesting thing that I noted in the beginning was that I felt like I was on camera all the time, and it made me feel a little self-conscious. Now, I don’t even remember that I’m on camera. It feels like I’m still in San Jose — for eight hours a day, I’m fully engaged in the business at Cisco’s headquarters.”
SUMMARY
Application Architectures There are four fundamental application architectures. In host-based networks, the server performs virtually all of the work. In client-based networks, the client computer does most of the work; the server is used only for data storage. In client-server networks, the work is shared between the servers and clients. The client performs all presentation logic, the server handles all data storage and data access logic, and one or both perform the application logic. With peer-to-peer networks, client computers also play the role of a server. Client-server networks can be cheaper to install and often better balance the network loads but are more complex to develop and manage.
World Wide Web One of the fastest growing Internet applications is the Web, which was first developed in 1990. The Web enables the display of rich graphical images, pictures, full-motion video, and sound. The Web is the most common way for businesses to establish a presence on the Internet. The Web has two application software packages, a Web browser on the client and a Web server on the server. Web browsers and servers communicate with one another using a standard called HTTP. Most Web pages are written in HTML, but many also use other formats. The Web contains information on just about every topic under the sun, but finding it and making sure the information is reliable are major problems.
Electronic Mail With e-mail, users create and send messages using an application-layer software package on client computers called user agents. The user agent sends the mail to a server running an application-layer software package called a mail transfer agent, which then forwards the message through a series of mail transfer agents to the mail transfer agent on the receiver’s server. E-mail is faster and cheaper than regular mail and can substitute for telephone conversations in some cases. Several standards have been developed to ensure compatibility between different user agents and mail transfer agents such as SMTP, POP, and IMAP.
